Mississippian, undifferentiated (MTMu;0)

State	Montana
Name	Mississippian, undifferentiated
Geologic age	Phanerozoic \| Paleozoic \| Carboniferous Mississippian
Original map label	Mu
Primary rock type	carbonate
Secondary rock type	fine-grained mixed clastic
Other rock types	medium-grained mixed clastic; chert
Lithologic constituents	Major Sedimentary > Carbonate (Bed)Most of the carbonates are limestone, but they often range to dolomitic. Minor Sedimentary > Clastic > Mixed-clastic > Conglomerate-sandstone (Bed) Sedimentary > Clastic > Mixed-clastic > Sandstone-Mudstone (Bed) Incidental Sedimentary > Chemical > Chert (Lense)
Map references	Ross, P.R., Andrews, D.A., and Witkind, I.J., 1955, Geologic map of Montana: U.S. Geological Survey, 2 sheets, scale 1:500,000.
Unit references	Ruppel, E.T., O'Neill, J.M., and Lopez, D.A., 1993, Geologic map of the Dillon 1o x 2o quadrangle, Idaho and Montana: U.S. Geological Survey Miscellaneous Investigations Series Map I-1803-H, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i1803H] O'Neill, J.M., Christiansen, R.L., 2002, Geologic map of the Hebgen Lake quadrangle: Montana Bureau of Mines and Geology Open File Report 464, 21 p, scale 1:100,000. Lewis, R.S., 1998, Preliminary geologic map of the Butte 1° x 2° quadrangle: Montana Bureau of Mines and Geology Open File Report 363, 16 p, scale 1:250,000. Berg, R.B., Vuke, S.M., 2002, Geologic map of the Fort Benton 30' x 50' quadrangle: Montana Bureau of Mines and Geology Open File Report 460, 7 p., scale 1:100,000. Porter, K.W., Wilde, E.M., 1993, Preliminary geologic map of the Lewistown 30' x 60' quadrangle, revised 1999: Montana Bureau of Mines and Geology Open File Report 308, 22 p., scale 1:100,000. Porter, K.W., Wilde, E.M., 1993, Preliminary geologic map of the Lewistown 30' x 60' quadrangle, revised 1999: Montana Bureau of Mines and Geology Open File Report 308, 22 p, scale 1:100,000. Lopez, D.A., 2001, Geologic map of the Sweet Grass Hills 30' x 60' quadrangle, north-central Montana: Montana Bureau of Mines and Geology Open File Report 443, 4 p., scale 1:100,000. Ruppel, E.T., 1998, Geologic map of the eastern part of the Leadore 30' x 60' quadrangle, Montana and Idaho: Montana Bureau of Mines and Geology Open File Report 372, 9 p., scale 1:100,000. Tysdal, R.G., Ludington, Steve, and McCafferty, A.E., 1996, Mineral and energy resource assessment of the Helena National Forest, west-central Montana: U.S. Geological Survey Open-File Report 96-683-A, 322 p., 6 plates. [http://pubs.er.usgs.gov/publication/ofr96683A] Harlan, S.S., Mehnert, H.H., Snee, L.W., and Meen, J.K., 1991, Preliminary isotopic (K-Ar and 40Ar/39Ar age determinations from selected Late Cretaceous and Tertiary igneous rocks in Montana, in Baker, D.W., and Berg, R.B., eds., Guidebook of the Central Wilson, A.B., and Elliott, J.E., 1997, Geologic maps of western and northern parts of Gallatin National Forest, south-central Montana: U.S. Geological Survey Geologic Investigations Series Map I-2584, 2 sheets, scale 1:126,720. [http://pubs.er.usgs.gov/publication/i2584] Mudge, M.R., Earhart, R.L., 1983, Geologic and structure maps of the Choteau 1° x 2° quadrangle, western Montana: United States Geological Survey Miscellaneous Geologic Investigations Series Map I-1300, scale 1:250,000. [http://pubs.er.usgs.gov/publication/i1300] Lopez, D.A., 2000, Geologic map of the Bridger 30' x 60' quadrangle, Montana: Montana Bureau of Mines and Geology Geologic Map 58, scale 1:100,000. Robinson, G.D. and Barnett, H.F., 1963, Geology of the Three Forks quadrangle, Montana, with sections on petrography of igneous rocks by H.F. Barnett: U.S. Geological Survey Professional Paper 370, 143 p. [http://pubs.er.usgs.gov/publication/pp370] Lonn, J., 2000, Geologic map of the Lima 30' x 60' quadrangle, southwest Montana: Montana Bureau of Mines and Geology Open File Report 408, 12 p., scale 1:100,000. Mudge, M.R., Sando, W.J. and Dutro, J.T., Jr., 1962, Mississippian rocks of the Sun River Canyon area, Sawtooth Range, Montana: American Association of Petroleum Geologists Bulletin, v. 46, no. 11, p. 2003-2018. Nichols, K.M., 1984, Stratigraphy of the upper part of the Madison Group, Sawtooth Range, northwestern Montana, in McBane, J.D., and Garrison, P.B., eds., Northwest Montana and adjacent Canada--Montana Geological Society 1984 Field Conference and Symposi Pearson, R.C., and Childs, J.F., 1989, Field trip guide, road log, and summary of Cretaceous volcanic geology, Dillon to Bannack, Beaverhead County, Montana: Northwest Geology, v. 18, p. 36-59. Wardlaw, B.R. and Pecora, W.C., 1985, New Mississippian-Pennsylvanian stratigraphic units in southwest Montana and adjacent Idaho, in Sando, W.J., ed., Mississippian and Pennsylvanian stratigraphy in southwest Montana and adjacent Idaho: U.S. Ge Zen, E-an, 1988, Bedrock geology of the Vipond Park 15-minute, Stine Mountain 7 1/2-minute, and Maurice Mountain 7 1/2-minute quadrangles, Pioneer Mountains, Beaverhead County, Montana: U.S. Geological Survey Bulletin 1625, 49 p., incl. geologic [http://pubs.er.usgs.gov/publication/b1625] Maughan, E.K. and Roberts, A.E., 1967, Big Snowy and Amsden Groups and the Mississippian-Pennsylvanian boundary in Montana, in Shorter contributions to general geology, 1966: U.S. Geological Survey Professional Paper 554-B, p. B1-B27. [http://pubs.er.usgs.gov/publication/pp554B] Sandberg, C.A. and Hammond, C.R., 1958, Devonian system in Williston basin and central Montana: American Association of Petroleum Geologists Bulletin, v. 42, no. 10, p. 2293-2334. Hayes, M.D., 1985, Conodonts of the Bakken Formation, Williston basin, North Dakota: The Mountain Geologist, v. 22, no. 2, p. 64-77. Sandberg, C.A. and Klapper, Gilbert, 1967, Stratigraphy, age, and paleotectonic significance of the Cottonwood Canyon Member of the Madison Limestone in Wyoming and Montana, in Contributions to general geology, 1967: U.S. Geological Survey Bulle [http://pubs.er.usgs.gov/publication/b1251B] Sandberg, C.A., 1967, Exshaw Formation of Devonian and Mississippian age in northwestern Montana, in Hayes, P.T., Changes in stratigraphic nomenclature by the U.S. Geological Survey, 1966: U.S. Geological Survey Bulletin 1254-A, p. A39-A41. [http://pubs.er.usgs.gov/publication/b1254A] Sando, W.J., and Dutro, J.T., Jr., 1974, Type sections of the Madison group (Mississippian) and its subdivisions in Montana: U.S. Geological Survey Professional Paper 842, 22 p. [http://pubs.er.usgs.gov/publication/pp842] Sando, W.J., 1982, New members of the Madison Limestone (Devonian and Mississippian), north-central Wyoming and southern Montana, in Stratigraphic notes, 1980-1982: U.S. Geological Survey Bulletin 1529-H, p. H125-H130. [http://pubs.er.usgs.gov/publication/b1529H] Sando, W.J., Sandberg, C.A. and Perry, W.J., Jr., 1985, Revision of Mississippian stratigraphy, northern Tendoy Mountains, southwest Montana, in Sando, W.J., ed., Mississippian and Pennsylvanian stratigraphy in southwest Montana and adjacent Shepard, Warren, 1993, Upper Mississippian biostratigraphy and lithostratigraphy of central Montana, in Hunter, L.D.V., ed., Montana Geological Society Annual Field Conference, 1993 field conference guidebook--Old timer's rendezvous edition; energy and m Gardner, L.S., 1959, Revision of Big Snowy group in central Montana: American Association of Petroleum Geologists Bulletin, v. 43, no. 2, p. 329-349. Derkey, P.D., Abercrombie, F.N., Vuke, S.M. and Daniel, J.A., 1985, Geology and oil shale resources of the Heath Formation, Fergus County, Montana: Montana Bureau of Mines and Geology Memoir no. 57, 100 p. Lidke, D.J. and Wallace, C.A., 1992, Rocks and structure of the north-central part of the Anaconda Range, Deerlodge and Granite Counties, Montana: U.S. Geological Survey Bulletin 1993, 31 p. incl. geologic map, scale 1:24,000. [http://pubs.er.usgs.gov/publication/b1993]
Geographic coverage	Beaverhead - Big Horn - Blaine - Broadwater - Carbon - Cascade - Deer Lodge - Fergus - Flathead - Gallatin - Glacier - Golden Valley - Granite - Jefferson - Judith Basin - Lewis and Clark - Liberty - Madison - Meagher - Park - Phillips - Pondera - Powell - Silver Bow - Stillwater - Sweet Grass - Teton - Toole - Wheatland